1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method therefor, and, in particular, to a semiconductor device in which a heat radiating member is provided for a substrate having a semiconductor element mounted thereon, and a manufacturing method therefor.
2. Description of the Related Art
Recently, along with an increase of an integration density of a semiconductor element, a heat amount generated from the semiconductor element increases. On the other hand, along with the increase of the integration density of the semiconductor element, an improvement of electrical characteristics of a circuit subsurface on which the semiconductor element is mounted is demanded. In order to satisfy these requirements, a semiconductor device is provided having a configuration in which, a heat radiating plate is disposed on a multilayer substrate, called EBGA (enhanced ball grid array), is provided (for example, see Japanese Laid-open Patent Applications Nos. 08-250529 and 2000-058702).
FIG. 1 shows an EBGA-type semiconductor device 1 as one example of the related art. This semiconductor device 1 generally includes a semiconductor element 2, a circuit substrate 3, a heat radiating plate 4, a sealing resin 5 and solder balls 6.
The circuit substrate 3 is a multilayer interconnection substrate, and includes a plurality of layers of interlayer interconnections 9. This circuit substrate 3 has a stair-step-shaped cavity provided at a center thereof. The heat radiating plate 4 is made of a metal material having good thermal conductivity. This heat radiating plate 4 is fixed to the circuit substrate 3 with the use of an adhesive sheet 8.
In the semiconductor device 1 shown in FIG. 1, the heat radiating plate 4 is mounted on the semiconductor element 2. Thereby, a heat generated from the semiconductor element 2 is radiated externally directly through the heat radiating plate 4. Thus, it is possible to increase the heat radiation efficiency. Further, wires 7 are applied to electrically connect between the semiconductor element 2 and the circuit substrate 3.
The sealing resin 5 is applied to fill the cavity in which the semiconductor element 2 is disposed. Thereby, the semiconductor element 2 and the wires 7 are sealed by the sealing resin 5. As a result, the semiconductor element 2 and the wires are protected. The solder balls 6 are disposed on a side of the circuit substrate 3 opposite to a side on which the heat radiating plate 4 is disposed.
In the semiconductor device in the related art described above with reference to FIG. 1, the adhesive sheet 8 made of a heat curing resin or a thermoplastic resin is applied to fix the heat radiating plate 4 to the circuit substrate 3. Specifically, the adhesive sheet 8 is placed on the circuit substrate 3, and also, on the adhesive sheet 8, the heat radiating plate 4 is disposed, first. Then, a thus-obtained intermediate product is heated during seconds at 200° C. Thereby, the heat radiating plate 4 is temporarily fixed to the circuit substrate 3. In this state, the adhesive sheet 8 is not yet hardened completely, and thus, the heat radiating plate 4 is merely temporarily fixed to the circuit substrate 3.
After the completion of the temporary fixing, permanent fixing processing is carried out in which the circuit substrate on which the heat radiating plate 4 is temporarily fixed is heated at a temperature on the order of 150° C. during hours, for example. A reason why such a long duration is required for the permanent fixing processing is that generation of voids in the adhesive sheet 8 otherwise occurring when rapid heating processing is carried out should be avoided. Also, an unnecessary stress should be prevented from being generated in the adhesive sheet 8. In order to positively avoid the generation of voids, the above-mentioned permanent fixing processing may be carried out in vacuo.
Thus, in the semiconductor device 1 according to the related art, the adhesive sheet 8 is required to fix the heat radiating plate 4 and the sealing resin 5, and also, the two times of heating processing should be carried out for fixing the heat radiating plate 4 and the sealing resin 5 with the use of the adhesive sheet 8. Further, in this permanent fixing processing, it is necessary to keep the heating condition on the order of 150° C. for hours. Thus, the efficiency of the fixing process for fixing the radiating plate 4 to the circuit substrate 3 is degraded. Thus, the semiconductor device 1 in the related art requires the many components/parts, and also, the manufacturing efficiency thereof is not high. As a result, the semiconductor device 1 becomes expensive.